1. Field of the Invention
The present invention relates to an axial flow fluid apparatus in which fluid flows axially, and blades are exposed into the fluid.
2. Description of Related Art
Among axial flow fluid apparatuses in which fluid flows axially, there is one in which a moving blade row and a stationary blade row are axially arranged. For example, a jet engine, a compressor, and a turbine can be mentioned.
The moving blade row includes a plurality of moving blades, and the stationary blade row includes a plurality of stationary blades. Also, in such an axial flow fluid apparatus, it is known that, as the moving blade row rotates, a velocity defect region where a stream of air is slow in comparison to surrounding regions is created on the downstream of the moving blades. The stream in this velocity defect region is generally called wake. The width of the stream becomes narrow, and the velocity defect becomes strong, and the velocity defect becomes strong just behind of the moving blades. Where the width of the stream becomes wide, the velocity defect becomes weak further away from the moving blades.
In an axial flow fluid apparatus in which a stationary blade row is installed on the downstream of the moving blade row, noise or vibration is generated as a wake resulting from the moving blades interferes with the stationary blade. It is known that this noise or vibration becomes large when the wake is strong, i.e. the velocity defect is large, and becomes small when the wake is weak i.e., the velocity defect is small.
Thus, for example, an invention which reduces the noise or vibration by widening the spacing between the moving blade row and the stationary blade row, utilizing the fact that the wake becomes weaker when further away from the moving blades, is disclosed in Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2003-227302).
Further, an invention and techniques in which the wake is weakened, and the noise or vibration is reduced by jetting the air introduced to the velocity defect region from the outside are described in Patent Document 2 (U.S. Pat. No. 6,004,095) and the following Non-Patent Documents 1 to 4.
Non-Patent Document 1:
‘Fan Flow Control for Noise Reduction Part 1: Advanced Trailing Edge Blowing Concepts’: AIAA (American Institute of Aeronautics and Astronautics) 2005-3025: Christopher Halasz etc.
Non-Patent Document 2:
‘Fan Flow Control for Noise Reduction Part 2: Investigation of Wake-Filling Techniques’: AIAA (American Institute of Aeronautics and Astronautics) 2005-3026: Matthew D. Langford etc.
Non-Patent Document 3:
‘Fan Flow Control for Noise Reduction Part 3: Rig Testing of Optimal Design’: AIAA (American Institute of Aeronautics and Astronautics) 2005-3027: Matthew D. Langford etc.
Non-Patent Document 4:
‘Low-Speed Fan Noise Reduction with Trailing Edge Blowing’: AIAA (American Institute of Aeronautics and Astronautics) 2002-2492: Daniel L. Sutliff
However, like Patent Document 1, when the spacing between the moving blade row and the stationary blade row is widened, the axial length of the axial flow fluid apparatus becomes long, and a casing or the like corresponding to the axial length is required. Therefore, the weight of the apparatus may increase or the apparatus may be enlarged. Further, if an increase in weight or enlargement of the apparatus is not allowed, the invention described in Patent Document 1 cannot be used.
Meanwhile, according to the invention described in Patent Document 2, and the techniques described in Non-Patent Documents 1 to 4, it is necessary to separately install a mechanism for introducing external air into the apparatus, and the mechanism may be complicated.